Wireless data exchange
Safety transmission via 5G
High reliability with minimal latency is just one aspect of the appeal of 5G. In particular, safety transmission via such a mobile network is proving to be a much-discussed topic. The next generation of the standard now promises a major step forward for wireless industrial data exchange. But will the requirements of industrial users actually be met, or is this still wishful thinking?
Historically, mobile communications technology was purely a consumer technology for communication in public networks, focusing on telephony, text messaging and later data forwarding. Previous applications for the remote maintenance of machines or the connection of remote process parts to a control system therefore had to make do without guarantees for latency, data throughput or network coverage.
In the new 5G standard, the interests of industry are now being taken into account in the specification for the first time. In addition to the classic focus on high data throughput (Enhanced Mobile Broadband, eMBB), the standardization also includes requirements for the Industrial Internet of Things (IIoT) - keyword: Massive Machine Type Communications (mMTC) - and time-critical communication (Ultra Reliable and Low Latency Communications, uRLLC). These functions are written down in several stages (releases) by the standardization organization Third Generation Partnership Project (3GPP).
Private mobile networks with short transmission paths
Apart from the functional innovations of the fifth generation of mobile communications, there is another innovation: the development of private mobile networks. Such networks have the same structure as public networks. The end devices (user equipment) communicate wirelessly with the radio towers (base station). In private networks, these are indoor or outdoor antennas with a similar design to WLAN access points. The base stations in turn connect to the central data center (network core) via radio relay or copper/fiber optic cables (backhaul). In private networks, the network core consists of local 19-inch equipment in the server room. It acts as the central communication element of the network and is responsible for routing user data to other wireless subscribers or forwarding it to the Internet as well as managing and authenticating the individual connections. It is important that the data transmission takes place in a private network located on the company premises. This ensures reliable communication with low latency and high reliability, as the transmission paths are short and the operator has full control over the network.
Many applications via one infrastructure
A private 5G network uses a licensed frequency band. This sets the technology apart from license-free solutions such as WLAN. Due to the exclusive use, the radio spectrum can be better controlled, the technology can be used more efficiently and the communication participants can be better prioritized. For example, there are no limiting framework conditions to ensure coexistence with other radio users in the license-free spectrum. 5G can make the most of this advantage, especially when there are many radio users in a small area. In addition, mobile radio allows considerably larger cells in outdoor applications. When it comes to covering airfields, ports or large process plants, this can be achieved with fewer base stations, which reduces cabling costs compared to traditional wireless solutions.
5G serves many applications via just one infrastructure. With the focus on eMBB, video applications, remote maintenance of machines or pioneering AR (augmented reality) solutions can be implemented. mMTC is particularly useful in logistics or facility management on site. For example, transportation aids can be monitored or consumption values such as water, electricity or gas can be transmitted to save energy. However, the main interest of users lies in the uRLLC functions for field communication: robots avoid the mechanical strain of trailing cables. Plant components can be rearranged without having to adapt the communication cabling. Automated Guided Vehicles (AGV) also exchange data with each other or with stationary sensors. It is conceivable that the entire intelligence of these participants could be outsourced to a central server system in order to reduce equipment costs and increase scalability.
Faster navigation thanks to additional information
In the previous examples, the focus is on safe data transmission from an AGV to a stationary safety sensor or other AGVs. If this is possible, the AGV no longer has to rely solely on the sensors installed on it, with which it can only drive on sight. With additional information from external sources, the AGV can now cross danger zones at full speed without colliding with a vehicle behind a bend or at a junction. The basis for this is safe fieldbus communication between the AGV's controller and other participants via the Profisafe protocol. Profisafe is a safety profile for the Profinet fieldbus.
The small packets of cyclical I/O data, which have to be forwarded at very short intervals with a high degree of reliability, are particularly critical for radio transmission. A timeout would lead to an emergency stop and the employees would have to manually reactivate the AGV. Furthermore, this communication is based on layer 2 of the OSI reference model. The data link layer of the model exchanges data via MAC addresses in a closed network and this information cannot be routed. However, data exchange via a current 5G network requires routing because the network operates on layer 3 and AGVs, robot cells or the production network represent a separate network. The third layer is the networking layer and works with IP addresses for exchange even beyond network boundaries. Data transmission must therefore take place via a layer 2 tunnel that connects the network of the AGV with the network of another AGV in the mobile network or wired production network. This tunnel encapsulates the data of the layer 2 connection in IP packets, which can then be routed to their destination to be decapsulated again. The tunnel should be as resource-efficient as possible so that no communication bottlenecks are created.
Reduce general costs
5G promises to be a major step forward for wireless industrial data exchange. However, there are still some challenges to overcome before 5G can be considered state of the art. The available hardware is not yet suitable for uRLLC communication. Current projects are already demonstrating the feasibility of Profisafe transmission between different participants with low latency via a layer 2 tunnel. However, the reliability for long-term operation in operational projects is not yet guaranteed. Particularly with Profisafe communication in an AGV application, latency peaks often result in interruptions that lead to an emergency stop. To solve this problem, hardware is required that is based on later releases and is currently under development.
The general costs of 5G technology will gradually fall over the next few years. At the same time, the range of smaller or larger private 5G networks for customized use in productive environments will increase. The challenges outlined are by no means a show stopper for the technology. The wide range of projects in different industries show the variety of applications that can be mapped using just one wireless technology. And uRLLC applications in the field of AGVs and robotics in particular already illustrate the potential of 5G in industrial communication.
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